The present invention relates to the activation of restraint devices in a vehicle. In particular, the present invention relates to the activation of restraint devices in a vehicle using explosive transfer lines, triggered from a central control unit.
There are various methods for restraining the occupants of a vehicle in the event of an accident. Many recent devices require the activation of a gas generating substance or material to inflate air bags or pretension seat belts. The initiation of the substances in these restraint devices typically requires the firing of a squib or initiator. In operation, one or more squibs can be activated using signals from sensors, which monitor such parameters as the rate of deceleration of the vehicle. When a predetermined rate of deceleration has been achieved, such a signal will ignite the squib by sending an electric current through it, thereby triggering the restraint device.
The squib is a relatively expensive component, and therefore an important factor in the cost of restraint systems. Additionally, systems using squibs require an electrical lead that carries the ignition signal(s) to each squib. In such an arrangement, monitoring the integrity of the connection to each individual squib requires that a low-level current be periodically provided through the electrical leads and the bridge wire of the squib. Because of the high cost of squibs, and the necessary complexity of their firing and monitoring systems, it would be advantageous to provide a vehicle restraint system that could be operated without the use of such devices.
Alternatives to the use of squibs for initiating the deployment of vehicle restraint devices have been proposed. In one such device, a laser diode mounted in the inflator of an air bag is used to ignite pyrotechnic material deposited adjacent to the propellent of the inflator. However, like the conventional system that uses squibs, the integrity of such a system is difficult to monitor.
Other proposed systems use a centrally located laser device, whose output is directed to a fiber optic cable. The fiber optic cable is then used to transmit the radiation from the laser to a charge located at the inflator. However, such systems are disadvantageous in that fiber optic cables are expensive, xe2x80x9cvery lossyxe2x80x9d (increases laser power requirement) and it is difficult to monitor their integrity.
Yet another method that has been proposed for initiating restraint devices in a vehicle relies on the use of explosive transfer lines. In such systems, a centrally located squib is used to initiate an explosive reaction in an explosive transfer line. After having been initiated, the explosive transfer line propagates the explosion started by the squib and carries it to the propellant of the inflator. Upon reaching the inflator, the explosion carried by the explosive transfer line initiates the inflator propellant, activating the restraint device. However, such systems have suffered from a number of disadvantages. For instance, such a system continues to depend on the use of squibs. As previously noted, squibs are expensive, thereby raising the cost of the restraint system, and in turn the cost of the vehicle itself. Also, explosive transfer lines have been expensive to produce, and have lacked a reliable method for verifying their integrity. Of course, in a safety system such as a vehicle restraint system, reliable operation is of primary importance.
Although the prior art describes systems and designs for triggering the operation of vehicle restraint systems, such as air bags and seat belt pretensioners, it would be advantageous to provide a system that did so at a lower cost. Concomitantly, such a system must be reliable and its integrity must be easily confirmed.
In accordance with the present invention, an apparatus for activating a selected one or more restraint devices located in a vehicle is disclosed. The apparatus includes a plurality of restraint devices, with a plurality of explosive transfer lines connected to the restraint devices. In one embodiment, the apparatus further includes a control unit, such as a central control unit, for use in activating each of the restraint devices. The central control unit has a housing, and includes a processor connected to a circuit board. Mounted to the circuit board are a plurality of initiator assemblies, each of which includes a circuit element. A first circuit element is operatively connected to the first explosive transfer line and the processor is used to control activation of the first circuit element, thereby igniting the first explosive transfer line.
The explosive transfer line can be formed from a first material that has unacceptable moisture resistance, and a second material that provides acceptable moisture resistance. The explosive transfer line may include a metalized layer for providing an electrical path for diagnosing the electrical continuity of the explosive transfer line. In one embodiment, the metalized layer has the property of providing acceptable moisture resistance for the explosive transfer line. The explosive transfer line can be further provided with an outer layer for providing abrasion protection. This outer layer is disposed outwardly of the metalized layer.
The circuit element of the present invention may include a laser diode, a bridge wire, a printed bridge, a semiconductor bridge device, a vapor deposited bridge or any other device for inducing pyrotechnic activation using an electrical signal. The initiator assemblies may include pyrotechnic material. In one embodiment, the explosive transfer line has pyrotechnic material deposited thereon in liquid slurry form. In a further embodiment, the circuit board is contained in the housing, and portions of at least the first explosive transfer line extend into the housing, while remaining portions of the first explosive transfer line extend away from the housing and toward a first restraint device.
Additional features involving use of explosive transfer lines in a vehicle for inflating an inflatable have been devised. Monitoring circuitry can be included for checking the continuity of each explosive transfer line. A hermetic seal can be provided with the control unit, instead of being associated with a squib located at the inflatable. A number of connectors can be utilized having different designs and desired functions. An end connector can be included adjacent to the restraint device for connecting the explosive transfer line thereto. Such an end connector can be serviceable or non-serviceable. When employed with a serviceable end connector, service personnel can readily disconnect the end connector and the explosive transfer line connected thereto from the restraint device. A transfer joint, such as a T-connector, can also be utilized when implementing a vehicle inflation system having a number of explosive transfer lines. The T-connector has three legs or members. In one embodiment, an explosive transfer line from the central control unit is held in one of the three legs, while two additional explosive transfer lines are held in the other two legs. The explosive transfer line from the central control unit activates the other two explosive transfer lines that are in operative communication with two restraint devices. A bridge connector interconnects or bridges two explosive transfer line portions and can be useful in extending the length that an explosive transfer line must have in order to be connected to a particular restraint device. With regard to installation of explosive transfer lines, elongated hollow members or tubes may be laid out in the vehicle along paths that are to be occupied by explosive transfer lines. The explosive transfer lines can be inserted or pushed through such hollow members easily and at convenient times. After insertion through a particular tube, the explosive transfer line can be properly held in place adjacent to the restraint device.
Based on the foregoing summary, a number of salient features of the present invention are readily discerned. A vehicle inflation system can be provided having centralized control over a number of restraint devices in a vehicle. The centralized control utilizes explosive transfer lines, rather than more expensive squibs that are conventional components of an inflator used to fill an air bag with gases. In one embodiment, the explosive transfer line has two materials, with one of the materials having unacceptable moisture resistance and the other material providing acceptable moisture resistance. Such a two layer design reduces costs over commonly used components. In another embodiment, the explosive transfer line has a metalized layer that may offer an electrical path for diagnosing electrical continuity in the explosive transfer line. Preferably, the explosive transfer line has an outer layer that protects the transfer line against abrasion. The system of the present invention is impervious to static electricity and RF energy initiations.
Additional advantages of the present invention will become readily apparent from the following discussion, particularly when taken together with the accompanying drawings.